This needs to be an odd number of rows / columns if you want the line to be central; additionally, an increased number of rows or columns will result in a smaller incline. Next, draw a transparent rectangle across the middle grid square:

I’m not saying the is the best, most efficient, or only way of doing this. However, it does mean that I can do it on both Windows Phone and Windows Store (and in WPF if I were so inclined) using a single shared project.

Basically, it’s not possible. However, this is the best (and only that works) workaround that I found.

Subclass the Listview

I tried everything. Absolutely everything.

I tried straightforward binding – that doesn’t work for IsSelected.
I tried using WinRT Xaml Toolkit – didn’t work.
I tried using Setters – they don’t work for WinRT.

Finally, I came across this solution; here’s the listview subclass (stolen directly from here: http://stackoverflow.com/questions/15994021/listviewitem-isselected-binding-works-for-wpf-but-not-for-winrt):